An automotive system such as a car stereo system, a navigation system or the like conventionally uses a sound effect to transfer information necessary for driving from the system to a driver of the vehicle.
For example, voice guidance from the navigation system and warning from various kinds of sensors and detectors on the vehicle to inform an obstacle on a road, abnormality in the vehicle or the like are output by using the sound effect for putting the driver in a precautionary state for appropriate operation (refer to Japanese Patent Document JP-A-2002-133596).
However, the sound effect for warning or the like does not necessarily serves as precautions when the driver is not well prepared to distinguish types of sound effects and does not know how to handle a situation by operating the vehicle properly without delay. For example, ultrasound sensors for obstacle detection disposed on four corners of the vehicle do not serve the driver properly when the warning sound effect of the sensor does not draw the driver's attention in an appropriate manner, that is, when the warning sound effect does not turn the driver's attention to a corner of the vehicle that is approaching an obstacle.